The present invention relates to material handling systems generally and portable radial stacking conveyor machinery in particular.
Conveyors adapted for handling sand, gravel, concrete, asphalt, coal, grain, ore, waste, earth, powders, granules, pellets, fuel, hulls, wood, bark, by-products, agricultural products, feeds, feedstocks, bulk material and other solids have been developed. A variety of belt type, preferably, and link type conveyors are offered for sale by commercial sources. Because linked conveyors and screw conveyors are the functional equivalent of belt conveyors for the purposes of the present disclosure, it is understood that references to conveyors are construed to include belt, link and screw conveyors. The choice of conveyor type often depends on the material for which it will be used to transfer. Belt conveyors move a cloth reinforced rubber belt over rollers and are used frequently to transfer and stockpile bulk material, especially material that is abrasive. Screw conveyors and bucket conveyors may be used with freely flowing materials and can lift vertically. Linked and paddle-type conveyors of various configurations intermediate between bucket and belt conveyors can be used to move materials an steeper inclinations than would be possible using flat belts.
Stockpiles may be created using conveyors that are often denominated stacking conveyors to distinguish them from transfer conveyors. The amount of material a given conveyor can stack is important in selecting equipment and locations. Increasing the length of a conveyor allows the height of the storage pile to increase with a resulting geometric increase in the amount of material stored. For example, Penterman discloses in U.S. Pat. No. 4,135,614 that increasing the height of a circular stockpile from 40 feet to 50 feet will nearly double the amount of material stored. Another way to increase the storage capacity is to form a radial stockpile. A radial stacking conveyor is a stacking conveyor that can be moved radially about a pintle or pivot point, denominated herein as center pivot, to increase the amount of bulk material that can be stockpiled at a site. Penterman further discloses that five to eight times as much material is stored in a 270 degree radial stockpile that has the same height as a circular stockpile. It could be economically advantageous to use a conveyor adapted for radial movement when the cost to do so is less than the cost of acquiring and operating the longer conveyor that would be required to store in a circular stockpile the amount of material that can be stored in a radial stockpile. For example, the foregoing reference states that a conveyor having a length of only 100 feet can store slightly more material in a 270 degree radial stockpile than can be stored in a circular stockpile using a conveyor that is 180 feet long.
When the bulk material handling needs at a particular site are temporary, it is often desirable to use portable conveyors. Agricultural products and road construction materials are examples of materials that may need to be temporarily stockpiled in large quantities at various locations from time to time.
Radial stacking conveyors can be portable and, in order to increase their portability, they may also fold or telescope. In order to be transported over public roads, a conveyor must be arranged so that it does not exceed the length and width restrictions of the locality in which the roads are situated. Although longer conveyors permit creation of larger stockpiles, shorter conveyors are transported more easily.
U.S. Pat. No. 4,135,614 to Penterman and U.S. Pat. No. 4,427,104 to Reid disclose foldable radial stackers. Rath discloses a telescoping radial stacking conveyor in U.S. Pat. No. 3,552,546. The maximum length of a radial stacking conveyor is limited, not only by its transport length, but also by the height to which the head section may be safely elevated. Radial stacking conveyors are usually supported by two wheels or two sets of wheels spaced apart from each other and the pivotable tail section. The spacing between the radial travel wheels must be sufficient to prevent the unit from tipping laterally when it is extended to its maximum operational length and height. The maximum distance by which the radial travel wheels may be separated is limited in practice by such factors as the requirement to narrow the equipment sufficiently for it to be transported over the public roads, the necessity to avoid covering the radial travel wheels with stored material, and the need to adequately weight or otherwise secure the tail section to prevent the head section from tipping down accidentally during operation. Previously available radial stacking conveyors that can be transported over public roads either require the use of escort vehicles during transport, lack stability, lack capacity, or cannot be converted quickly and efficiently between the transport and the operational configurations. In addition, previous portable radial stackers have failed to provide adequate horizontal distance between the radial travel wheels to accommodate conveyors of lengths now desirable.
Another problem with previously available portable radial stackers is that they have been susceptible to breakdown during transport over uneven roads. The great length of a radial stacking conveyor configured for transport can cause abnormal tensile loads at the towing hitch point and excessive fatigue and stress during transport over uneven surfaces and bumpy highways. The problem is exacerbated when a very long conveyor is fitted with a single transport axle located midway along its length.
Earlier portable radial stackers that perform comparably to the present invention have all required the expenditure of a substantial amount of labor and time to convert between transport and operational configurations. The effort required to convert between operational and transport configurations can be a substantial cost item and consume scarce skilled labor resources. Costs for equipment tear-down, relocation and set-up often contribute substantially to the cost of any temporary materials-handling job and could preclude the undertaking of otherwise desirable projects. Those costs are minimized by the present invention.
Not only is conversion between configurations faster, the present invention requires no jacking or other direct manipulation of machine structural support members by the operator to effect conversion. Most of the portable radial stackers previously disclosed appear to be less stable during the process of converting between the transport and operational configurations. No step of the procedure used by the present invention for converting between operational and transport configurations is known to compromise conveyor stability.
Yet another limitation of previously known radial stackers is the difficulty of adequately and properly controlling the radial motion to enable the desired degree of control over the stacking process.
What is needed is a portable radial stacking conveyor:
1. that can be converted swiftly and safely between transport and operational configurations; PA1 2. that provides greater lateral stability in operation by configuring the radial travel wheels to have optimally wide horizontal separation; PA1 3. that is narrow enough to be transported over public highways without escort vehicles; and PA1 4. that has better durability than earlier portable radial stackers.
Fifteen minutes is ample time for an operator to convert the present invention between the transport and the operational configuration. Other systems require substantially more labor to convert and longer times to set-up. The present invention fulfills the other needs that remain unmet by previously known portable radial stacking systems whether they use belt, screw, bucket, paddle, link-belt, or other conveying mechanisms, all of which are defined as equivalent in this specification.
The invention disclosed herein provides a wider base during operation than does any portable radial stacker previously available commercially. It can be converted from the transport configuration to the operational configuration in a matter of minutes without the necessity of jacking, blocking, or removing any structural support components.
The radial stacker of the present invention is equipped with brakes, preferably air brakes, and may be towed by a truck tractor or other vehicle. The transport wheels are preferably dual tandem wheels having a maximum width of 11 feet-51/2 inches fitted to an underslung axle walking beam bogey on each end of an elongated member which may be solid, angled, or, preferably, a tubular axle. Use of walking beams to connect the transport wheels to the conveyor reduces the vertical displacement of the load by half when the apparatus encounters irregularities in the road surface and, as a result, greatly reduces the amount of stress and fatigue to which the equipment is exposed during transport. The design and construction of the underslung axle walking beam yields several important advantages: optimum machine height, improved stability, better obstruction clearance during transport, improved operational clearance for outriggers, and better attachment locations for connecting hydraulic cylinders used for outrigger operation.
The radial travel wheels are mounted to outriggers that pivot, or retract, upward for transport and pivot, or extend downward for stacking. Although the outriggers may be fashioned having any length, they are preferably of a length to result in an overall width of 22 feet-6 inches when configured for stacking. The dual radial travel wheels are mounted on rocker spindles and may optionally be equipped with a hydraulic drive motor to move the conveyor radially. This dual wheel/rocker spindle configuration adds stability by using flotation tires and by providing an inherently even weight distribution over each tire regardless of the conveyor angle with respect to the ground. The rocker spindle is underslung to improve stability of the system and to allow optimal spacing of the hydraulic cylinder pin points; for that reason, the hydraulic system operates at lower pressures than would otherwise be the case.
To operate the invention, a radial pivot plate is placed at the desired location for the radial stacker center pivot. Any needed electrical connection is made and the hydraulic pump started. Gasoline, diesel, or, preferably, an electric motor can supply power to the hydraulic pump. The outriggers are next, preferably hydraulically, or mechanically, pivoted, and thereby extended, downwardly and outwardly from the longitudinal axis of the conveyor to lower the radial travel wheels to a distance of approximately one inch from the ground. Any removable, foldable or telescoping sections are fitted and extended starting with the tail section to prevent tipping. The conveyor tail section anchor pivot is attached to the radial pivot plate which is fixed to a selected location on the ground to allow the conveyor to be moved radially about the center pivot during operation. The conveyor may then be raised to the desired height, either mechanically or, preferably, hydraulically. Finally, the outriggers are extended further downward to raise the transport wheels from the ground slightly and allow radial movement. The procedure is reversed to ready the conveyor for transport.
It is part of the preferred embodiment of the present invention to have all operational controls at a single location, to deliver all motive force hydraulically, and to operate all hydraulic devices from a single pump and reservoir. However, it is possible to use other configurations such as a series of dedicated pumps, reservoirs, and dispersed controls without departing from the scope of the invention. Similarly, in this preferred embodiment, the hydraulic cylinders are each fitted with check valves as a safety precaution although omission of the check valves or substitution of other safety mechanisms such as mechanical locks or stops would not depart from the scope of the invention.
It is further to be understood that existing conveyors may be retrofitted to embody the present invention or it may be included with newly manufactured conveyor systems.